1. FIELD OF THE INVENTION
This invention relates generally to release agents and methods of releasing products from containers and more particularly to an improved biodegradable release agent for hot-mix asphalt and methods including the application of such release agents to coat the container or other equipment for the hot-mix asphalt.
2. BRIEF DESCRIPTION OF THE PRIOR ART
In the transporting and handling of hot-mix asphalt, it has been necessary to treat the dump truck or trailer with a suitable release agent to prevent the asphalt-mix from sticking to the walls thereof Petroleum oils have been used to coat the walls of trucks or trailers for this purpose. Recently, the use of petroleum oils as release agents has been criticized and, in some places, prohibited because of environmental concerns. Consequently, the industry has had a need for an environmentally acceptable release agent for dump trucks and trailers for transporting hot-mix asphalt.
There are several patents which illustrate the need for release agents in different applications.
Aron U.S. Pat. No. 3,437,621 discloses a composition comprising an oleate salt of a metal, a potassium salt of a fatty acid, a fatty acid, a polyethylene glycol ester or ether, an alkylglycol, or a derivative thereof, a high molecular weight alkylol, and a paraffin which is used as a mill release agent for rubber bases.
Kekish U.S. Pat. No. 4,312,901 discloses a method for reducing the tendency of coal to freeze and thus adhere to the sides of metal storage and shipping containers used to store and/or transport coal at temperatures below the freezing point of water which comprises applying to the sides of the container a coating composition comprising a hydrocarbon liquid and a hydrocarbon oil-soluble liquid having an HLB value of 1-8.
Blahak U.S. Pat. No. 4,312,672 discloses a release agent applied to the surface of a mold to permit ready removal of plastic, particularly polyurethane, from the mold. The release agent contains a film-forming substance having an affinity to the plastic and becomes attached to the plastic and is removed therewith on removal from the mold.
Dwivedy U.S. Pat. No. 4,898,751 discloses methods and compositions of matter (e.g., mineral or vegetable waxes) for inhibiting and/or preventing the formulation of adhesion of materials such as coal, mineral ores, taconite, glass and others to the container (railcars, silo, hopper bins, etc.) walls due to freezing temperatures in winter and/or excessive moistures during the rest of the year.
The present invention is distinguished over the prior art in general, and these patents in particular by providing an improved method of prevention of adhesion of hot-mix asphalt to dump trucks and other containers or equipment which comprises preparing an aqueous dispersion of a vegetable oil and applying the dispersion to the surface of the container before loading the hot-mix asphalt therein. Vegetable oils which are useful as release agents in aqueous dispersion include cottonseed oil, soya oil, rate (canola) oil, peanut oil, corn oil, sunflower oil, palm oil, coconut oil, and palm kernel oil. The oil is emulsified in water, using a suitable emulsifier, preferably a sorbitol base emulsifier, in the amount of 1-5 oz. per gallon of water. The oil and emulsifier are preferably premixed and supplied as a self-emulsifiable composition. The resulting emulsion is applied in an amount to provide a thin coating on the wall of the container. The emulsion is applied in the amount of 3-4 qts. to coat a dump truck or 4-6 qts. to coat a trailer. The hot-mix asphalt is easily removed from the container, i.e., truck or trailer, or other equipment without sticking and the release agent has been found to be completely biodegradable.